The invention relates to a linear guide device, comprising a guide rail with a longitudinal axis and at least one guideway, and a runner assembly guided at the guideway, of which there is a least one, in the direction of the longitudinal axis.
Contaminants on the guideway may impair the smooth running and guide precision of the runner assembly and cause premature wear. These contaminants may come from hot chips which are produced in cutting machine tools and come to lie on the guideways, in which case there is even a risk of the chips burning into the guideways. Other contaminants are particles of dirt and dust, which may settle on the guideways. If they mix with coolants or lubricants, this may produce an abrasive mixture which, if it enters the runner assembly, may cause abrasion at the guideways and the guide members of the runner assembly. Although conventional runner assemblies are frequently sealed off all round from the guide rail, the possibility of contaminants entering the interior of the runner assembly cannot be entirely ruled out. For it is often not possible to prevent microroughness in the guide rail surface and at the sealing elements which are used. The contaminants may then penetrate through such microroughness to the interior of the runner assembly.
It is known to cover the guide rail by a bellows which is coupled in terms of movement to the runner assembly in order to provide protection against contaminants, as presented, for example, in a prospectus of the company Deutsche Star entitled xe2x80x9cSchienenfxc3xchrungstischexe2x80x9d (xe2x80x9cRail guide tablesxe2x80x9d), number RD 82501/06.96. However the material of the bellows may easily scorch because of hot chips, which is why telescopically retractable and extensible covering mechanisms have been resorted to for applications in which a high incidence of hot chips is to be expected. However these mechanisms entail a high expenditure. The bellows and telescopic covering also require storage space, which reduces the available travel of the runner assembly.
Also known from DE 43 34 311 A1 is a covering solution in which a guide rail is mounted in a U-shaped profiled housing on the bottom thereof and the longitudinal opening of the housing is closed by a cover strip which lies against the mutually opposite side walls of the housing. This solution offers reliable protection against the penetration of contaminants into the interior of the housing, although depends on the presence of the U-shaped profiled housing and is therefore only suitable for special applications.
The object of the invention is to present a covering solution which is suitable for a broad field of application of the linear guide devices and which affords reliable protection against contaminant-induced impairments of the guide quality of the linear guide device.
A linear guide device comprises a guide rail with a longitudinal axis and at least one guideway. A runner assembly is guided at the guideway, of which there is a least one, in the direction of the longitudinal axis.
The guideway is coveredxe2x80x94in the direction of the longitudinal axisxe2x80x94on both sides of the runner assembly substantially over the respective entire usable remaining length by a cover strip which lies against at least one cover strip contact zone of the guide rail or is so close to said cover strip contact zone as to prevent contaminations to reach said cover strip contact zone without xe2x80x9creal body contactxe2x80x9d. The cover strip preferably lies, however, directly against the guide rail. There is as a result very little dependence on the constructional installation conditions of the linear guide device, irrespective of whether this is constructed with or without a U-housing for example. In addition, as it is not necessary for the cover strip to be compressed and expanded like bellows, it may be made of a material which is sufficiently insensitive to hot chips. The covering solution according to the invention entails a distinctly lower construction expenditure than the above-mentioned telescopic coverings.
The cover strip contact zones and the guideway may basically correspond, at least in part. Optimum adaptation of the cover strip contact zone to the requirements of the cover strip, especially as regards the tightness of the system, without having to take account of the specific configuration of the guideway, can be achieved by the cover strip contact zone and the guideway differing, at least in part.
Optimum preservation of the guideway is achieved if the cover strip covers the guideway in contact-free fashion and lies against cover strip contact zones of the guide rail which are located transversely to the longitudinal axis on both sides of the guideway. This can easily be achieved by disposing the guideway in a depression in the guide rail which is covered by the cover strip and is formed between the cover strip contact zones.
Generally speaking, the opposite cover strip contact zones will comprise large-side contact zones against which the cover strip lies at its large side which faces the guideway., In this case it is advisable for the large-side contact zones to be formed by plane, coplanar contact faces. The cover strip can thus lie flatly and tightly against the guide rail.
However it is also possible for at least one cover strip contact zone to be formed as a narrow-side contact zone against which the cover strip lies at its narrow sides. There is no possibility of the aligning function of the narrow-side contact zones causing the cover strip to slip and possibly expose the guideway locally, in particular when mutually opposite narrow-side contact zones are formed at the guide rail for both narrow sides of the cover strip.
The linear guide device may be installed in such a way that the cover strip lies against axe2x80x94in the installed position vertically lower side of the guide rail and is consequently at risk of separating from the guide rail, if it is not tensioned with sufficient tautness, and allowing dirt to penetrate to the guideway. It is expedient, in particularxe2x80x94although not exclusivelyxe2x80x94in a case of this kind to provide securing means at the guide rail and/or at the cover strip which secure the cover strip to the guideway outside of the region of the runner assembly in the covering position. This may be achieved, for example, by the possibility of frictionally clamping the cover strip between mutually opposite narrow-side contact zones. Alternatively to or in addition to this, it may be possible to positively secure the cover strip in its covering position at the guide rail by, for example, undercutting the narrow-side contact zones for the engagement of the narrow sides of the cover strip. The cover strip may be retained with some play in the undercuts of the narrow-side contact zones. However it may also be clamped at its narrow sides or/and at its large sides. The cover strip may also be secured by locking means which, rather than passing over the entire length of the guide rail, are formed just locally and distributed over the length of the guide rail.
The runner assembly may be constructed in end regions with strip curvature means which give the cover strip a forced curvature facilitating its entry between mutually opposite narrow-side contact zones and therefore reducing the distance between the narrow sides of the cover strip. The curvature of the cover strip may be of assistance in enabling it to be easily introduced into undercuts of the guide rail by way of its longitudinal edges. It is in this case possible for the cover strip to completely uncurve again after being introduced into the undercuts. If, on the other hand, the cover strip is to be frictionally clamped at its narrow sides, it is advisable to adapt the width of the cover strip to the securing means such that the cover strip is pre-curved in the covering position.
According to a further variant, the securing means may also be achieved by the possibility of retaining the cover strip in the covering position through magnetic means.
The guideway and the cover strip are preferably formed together at a rail body of the guide rail which is of a uniform base material, and the rail body may undergo purely secondary hardening or/and coating operations in the region of the guideway or/and of the cover strip contact zone in order, for example, to improve the quality of the guide rail and its load-bearing capacity. The guideway and the cover strip contact zone may in particular be disposed at the rail body of an integrally coherent material, although it is basically also possible for the guideway and the cover strip contact zone to be formed at rail sub-bodies which, although of the same base material, are separate.
The guide rail frequently comprises two or more guideways rather than just one. In this case it is advisable for the guide rail to comprise at least two guideways extending parallel to one another and being jointly covered by the cover strip.
The invention is particularly applicable to guide rails which comprise a fastening face, a top face lying opposite the fastening face and two side faces connecting the fastening face to the top face, with at least one respective guideway being formed in each of the side faces and at least one respective cover strip being provided at each side face for the associated guideway, of which there is at least one. In this case it is particularly favorable if, when there are at least two respective guideways in each of the side faces, all the guideways of each of the side faces are covered by a respective common cover strip.
The cover strip may comprise a metallic material, in particular steel. It may also comprise a plastics material. In this case the possibility of producing the cover strip from different materials, possibly with a metallic core, which provides the desired strength, and a jacket of a plastics material or rubber, which provides a good seal between the cover strip and the guide rail, is not to be excluded.
The invention is basically suitable for all types of guidance of the runner assembly on the guide rail. Thus the runner assembly may be guided in sliding fashion on the guideway formed as a slideway. The runner assembly may equally be guided in rolling fashion on the guideway formed as a rolling track. In the latter case the runner assembly may be guided on the rolling track by at least one roller rotatably mounted on the assembly. It is, however, also possible for the runner assembly to be guided on the rolling track by at least one row of rolling bodies circulating along a continuous circulation path.
The cover strip may be fastened to the runner assembly to move together with the latter along the longitudinal axis. It may be deflected in the region of the rail ends at deflection means and closed to form a loop by a returning strip section. It is basically also possible to provide two take-up rolls in each case in the region of the rail ends, from or onto which the cover strip can be unwound or wound, according to the direction of movement of the runner assembly. The cover strip may even exhibit longitudinal elasticity.
According to a preferred embodiment, the cover strip runs over a support face arrangement of the runner assembly in sweeping fashion at its large side which faces the guideway, and the runner assembly comprises approach means which retain the cover strip before and after the support face arrangement in the longitudinal direction close to the guide rail. Although it is basically possible for two guideways disposed on opposite sides of the guide rail to be covered by a closed cover strip loop which is stationary with respect to the guide rail, it is preferable for the cover strip to have free strip ends which are retained at the guide rail ends, which are spaced apart in the longitudinal direction. In this respect it is advisable if at least one of the strip ends can be anchored in an anchorage block which is supported at an axial front face of the associated rail end, as it is thus possible to avoid additional machining of the guide rail. It is expedient if two cover strips disposed at opposite side faces of the guide rail can be anchored in the anchorage block.
Mounting is facilitated by a solution in which the anchorage block can be fitted axially on the associated rail end and for this purpose comprises at least one axial plug part by which it engages axially over the guide rail at its outer circumference.
The cover strip can preferably be tensioned by tensioning means which are disposed in the region of at least one rail end. It is in this case possible for the tensioning means to comprise adjustable tensioning components. The tensioning means may also comprise at least one resilient tensioning component. Spring preloading can compensate for temperature-induced changes in the length of the cover strip. It may in addition prevent jerky tensile forces at the cover strip if stick-slip effects between the cover strip and the runner assembly occur.
In a preferred embodiment, the runner assembly comprises a runner which is responsible for its guidance on the guide rail, with the approach means being disposed at least at one strip guide unit which can be mounted on the runner. The runner may be a commercially available series-produced component which can be adopted to form the runner assembly substantially without being modified. This applies in particular if the support face arrangement is disposed at least in part, in particular entirely, at the strip guide unit, of which there is at least one. In terms of mounting, it is favorable if fastening members serving to assemble the runner are also constructed for mounting the strip guide unit. For example, fastening screws which serve to fasten top units of the runner to a main body of the latter may be provided with an additional thread serving to subsequently mount the strip guide unit on the pre-mounted runner.
A respective strip guide unit is expediently mounted at axially opposite end faces of the runner. These may have an outer contour whichxe2x80x94viewed in the axial direction away from the runnerxe2x80x94narrows as the distance from the runner increases, so that the runner assembly has a pleasant exterior.
The cover strip is expediently guided past the runner on the outside. It is then advisable to protect the cover strip against damage by a guard bow which is mounted on the strip guide unit, of which there is at least one.
The runner assembly may bear at least one lubricant dispenser for lubricating the cover strip in order to reduce the friction between the cover strip and the approach means as well as the support face arrangement. This lubricant dispenser may comprise a lubricating body which contains lubricant and is in lubricating contact with the cover strip. The lubricating body may at the same time be in lubricating contact with at least one guideway covered by the cover strip. This lubricating body is appropriately disposed in a strip guide unit which may also be configured so as to additionally accommodate a lubricant reservoir which is connected for supply purposes to the lubricating body, of which there is at least one. The lubricating body may take over at least a part of the strip guide function of the strip guide unit.